Yesterday, the Nevada State Athletic Commission confirmed 14 of the 15 fighters who underwent drug testing for “UFC 125: Resolution” produced negative results. However, there was one sample from an unnamed contestant they were unable to clear.

While NSAC executive director Keith Kizer wasn’t prepared to share who the mystery man was, Thiago Silva admitted to a popular Brazilian website one of his two urine samples registered a positive result. However, the light heavyweight claims he’s done nothing wrong.

The NSAC traditionally tests all main card athletes, all winning fighters and any competitors who previously failed drug tests. However, all contestants are subject to random screenings.

All athletes were tested for substances of abuse (such as marijuana and cocaine), as well as anabolic steroids and other performance-enhancing drugs.

Kizer told multiple news outlets they were waiting for Silva’s second sample to return from the lab. No timetable was given for his results.

It was reported Wednesday Silva would be forced to pull out of his UFC 130 scrap against Quinton “Rampage” Jackson with an undisclosed injury. Rashad Evans is the front runner to replace him, however his management has denied receiving an offer to rematch Rampage.